CCSS patch:regular vs.extraordinary Blue:regular Red:extraordinary Control mesh Limit surface Assume each mesh face in the control mesh ■a quadrilateral at most one extraordinary point (valence n is not 4) An interior mesh face F in the control mesh-a surface patch S in the limit surface Regular patch:bicubic B-spline patches,16 control points Extraordinary patch:not B-spline patches,2n+8 control points CCSS patch: regular vs. extraordinary  Assume each mesh face in the control mesh ◼ a quadrilateral ◼ at most one extraordinary point (valence n is not 4)  An interior mesh face in the control mesh → a surface patch in the limit surface ◼ Regular patch: bicubic B-spline patches, 16 control points ◼ Extraordinary patch: not B-spline patches, 2n+8 control points Control mesh Limit surface S F Blue: regular Red: extraordinary